Process for the production of alloys of lead with alkaline earth metals



Patented Mar. 26, 1929.

UNITED STATES.

PATENT OFFICE.

GUILLAUME JUSTINE KROLL, OF LUXEMBURG, LUXEMBURG.

PROCESS FOR THE PRODUCTION OF ALLOYS 0]? LEAD WITH ALKALINE EARTH METALS.

No Drawing. Application filed December 20. 1926, Serial No. 156,072, and in Germany December 29, 1925.

This invention relates to a process for the production of alloys of lead with alkaline earth metals.

As is well known it is possible to obtain alloys of lead with the alkaline earth metals by heating lead with carbides of the alkaline earth metals or with mixtures forming such carbides. Owing to its high affinity for lead the alkalineearth metal is simply dissolved out from the carbide, leaving the carbon. This solution process requires a temperature of about 1300 0., when the operation is carried out in graphite crucibles with access of air. At this temperature lead already possesses a considerable vapour tension so that the workmen are exposed to the danger of poisoning by lead fumes. A further disadvantage of the above described process is that at the most, only 25% of the alkaline earth metal contained in carbide is dissolved out and that the amount of lead run out only amounts at a maximum to 92% of the starting material.

Practical examination of this process has moreover shown that it is impossible to carry it out as a continuous operation wherein the lead must be heated in graphite crucibles for a prolonged period at about 1300 C. After a short time the porous crucibles allow the liquid highly heated lead to penetrate there through.

It has now been found that the aforesaid disadvantages of the carbide process can be obviate-d by certain measures. In the first placeit is important to decrease the temperature. A correct recognition of the reaction taking place during this solution process, has shown that it is above all necessary to exclude the oxygen and nitrogen of the air. .At temperatures upwards of about 1100 C., these gases have an extraordinarily energetic oxidizing and nitrating action upon the carbide which iscovered by a protective layer which prevents penetration of the lead, with the re- Sult that the solution process gradually ceases. A y

If, however the carbide is heated together with the lead in an atmosphere of hydrogen, the solution of the alkaline earth metal already actively commences at about 800 C.-

The carbide is much more completely used up and the yield in alloy is much better.

For example a mixture of 1000 grammes lead with 50 grammes calcium carbide which had been heated for one hour at 800 (1, with constant stirring yielded an alloy containing 2.1% calcium. The yield amounted to about 75% of the calcium contained in the carbide and 97% of the lead employed.

The heating may also be effected in an atmosphere of other gases such as argon or even carbon monoxide instead of in hydrogen, as

long as such gases remain more or less inert,

towards carbide at the temperature range in question. It is moreover sutlicient to evacuate the reaction vess'els or to close them airtightly or, in addition, to tighten them with charcoal in the way usual when glowing copper. Any measure for excluding the oxygen or the nitrogen of the air leads to the desired end, namely the reduction of the solution temperature.

It is only by means of the above described measures that it has been possible to carry out thecarbide process for the production of alloys of lead with alkaline earth metals on a practical scale.

The working temperatures used range from 700 to a maximum of 1000" C., so that the employment of iron crucibles was rendered possible. The using up of the carbide and the removal of the metal could be improved to such an extent that the production of intermediate products is inconsiderable, When employing electric furnaces for heating the charge, considerable current economy was obtained.

I claim 1. A process for the production of alloys of lead with alkaline earth metals which comprises heating lead at a reacting temperature not excecding 1100 C. with alkaline earth metal carbides in the absence of substances which form around the carbides a protective layer impenetrable by lead.

2. A process for the production of alloys of lead with alkaline earth metals which comprises heating lead at a reacting temperature not exceeding 1100 C. with alkaline earth metal carbides in the absence of oxygen and nitrogen.

3. A process for the production of alloys of lead with alkaline earth metals which comprises heating lead at a reacting temperature not exceeding 1100 C. withalkaline earth metal carbides in a closed container impermeable to air.

4. A process for the'production of alloys of lead with alkaline earth metals which comprises heating lead at a reacting temperature not exceedlng 1100 C. with alkaline earth metal carbides in an evacuated closed container.

5. A process for the production of alloys I of lead with alkaline earth metals which comprises heating lead at a reacting temperaturenot' exceeding 1100 C. with sub-' stances adapted to form alkaline earth metal carbides, said heating being effected in the absence of substances which form around the carbides a protective layer impenetrable by lead.

6. A process for the production of alloys of lead with alkaline earth metals which comprises heating lead at a reacting temperature not exceeding 1100 C. with substances adapted to form alkaline earthmetal caradapted to form alkaline earth metal carbides, said heating being effected in a closed container impermeable to air.

8. A process for the production of alloys of lead with alkaline earth metals which comprises heating lead at a reacting temperature not exceeding 1100 C. with substances adapted to form alkaline earth metal carbides, said heating being effected in an evacuated closed container.

9. A process for the production of alloys of lead with alkaline earth metals which comprises heating lead at about 700 C. to 1100 C. with alkaline earth metal carbides in' the absence of substances which form around the carbides a protective layer impenetrable by lead.

10. A process for the production of alloys M of lead with alkaline earth metals which comprises heating lead at about 700 C. to 1100 C. with substances adapted to form alkaline earth metal carbides, said heating bein eflected in theabsence of substances whic form around the carbides a protective layer impenetrable by lead.

In testimony whereof I aflix my signature.

GUILLAUME JUSTINE KROLL. 

